CONFORMATIONAL PREFERENCES OF THE CALLIFMRFAMIDES AND THEIR FREE-ACIDANALOGS

A molecular dynamics study was undertaken to determine the conformatio nal basis for the differing activities of the insect neuropeptide horm ones calliFMRFamide 3 (SPSQDFMRF-NH2), calliFMRFamide 5 (APGQDFMRF-NH2 ) and their corresponding free-acid analogues (SPSQDFMRF-OH and APGQDF MRF-OH) in two insect bioassays. A simulated annealing protocol was us ed to determine the range of conformers available to the linear peptid es. Analysis of the conformers obtained indicated that all the peptide s exhibited distinct secondary structure preferences. These, when corr elated with their biological activities, enabled the formulation of pu tative conformation-activity relationships for the peptides.